The Pentagon, for instance, has major air bases in Qatar, Kuwait and the United Arab Emirates. The rulers of those countries are Sunni Muslims and are generally leery of Iraqi Prime Minister Nouri al-Maliki, a Shiite whom the White House has criticized for exacerbating sectarian tensions.

""Militarily, we can do just about anything we want," said David Deptula, a retired Air Force lieutenant general who helped lead previous air campaigns over Iraq and Afghanistan. "The question is, to what end?""

"As Mr. Obama pursues a political solution, officials said Vice President Joseph R. Biden Jr. and Secretary of State John Kerry would both play higher-profile roles. Mr. Biden, who held the Iraq portfolio during the administration's first term, called Mr. Maliki last week. The president has not yet spoken to the Iraqi prime minister during this crisis."

"At the federal level, the impeachment process is a two-step procedure. The House of Representatives must first pass, by a simple majority of those present and voting, articles of impeachment, which constitute the formal allegation or allegations. Upon passage, the defendant has been "impeached". Next, the Senate tries the accused. In the case of the impeachment of a president, the Chief Justice of the United States presides over the proceedings. For the impeachment of any other official, the Constitution is silent on who shall preside, suggesting that this role falls to the Senate's usual presiding officer. This may include the impeachment of the vice president, although legal theories suggest that allowing a defendant to be the judge in his own case would be a blatant conflict of interest. If the Vice President did not preside over an impeachment (of anyone besides the President), the duties would fall to the President pro tempore of the Senate."